An Overview of Human Longevity
In fifth grade, I read the novel Tuck Everlasting. The story centered around a family who drank from a magical spring that gave them the ability to live forever. After finishing the book, I wondered about immortality. At the time, living forever seemed pretty great. After all, why would anyone want to die? But, the story of the Tuck Family portrayed immortality to be some sort of a curse. The family faced the loss of everyone they loved while they continued living and lacked a normal life. I took that story to heart, and as I’ve gotten older I’ve realized that there’s a cycle to life, which at some point must come to an end. However, I will admit that if I could live in good health with my friends and family for much longer, then I would definitely want to. I’ve always imagined everything that we all could accomplish if there was no limit to life. So now, 5 years later, I’m researching human longevity to understand what it would really mean for us to extend the human lifespan.
What is Longevity and What Does it Entail?
First of all, it’s important to acknowledge that human longevity does not necessarily mean living forever. The end of biological aging does not mean the end of death. Because, it’s not about living forever, it’s about extending our lifespans to be able to enjoy them longer.
For most, a lifespan is perceived to be just how long you live. However, this common way of looking at time is insufficient. A lifespan is much more of a measurement of existence rather than living. To understand this concept, let’s put life into perspective:
The average global life expectancy is around 73 years old. To break it down, on average 21 years of your life are spent growing up and going to school. The next 45 years are spent raising a family and working a day job. Let’s say you retire in your 60s. That gives most people 15 years to do whatever they want. But, more than half of adults over the age of 65 face health issues that don’t allow them to live their lives to the fullest. At that point you’re just existing, not living.
So, we can see that living longer is pointless if you spend most of your free years combatting illness and health problems. The goal of human longevity is to enable not only a longer lifespan, but also a healthier one. Meaning, that in conjunction with a lifespan, what’s really at stake here is your health-span.
Aging:
The modern-day human race constantly tries to stay young, both mentally and physically. We stress the importance of eating healthy and exercising, and we as a society buy into all of those “anti-aging” beauty products. Essentially, all we want is to stay young forever. The key word here is “young.” Living longer isn’t the problem, aging is.
You may be surprised to hear that we have already increased our life expectancy. A report from Our World in Data showed that a 5-year old in 1841 had a life expectancy of 55 years. Today, the same child can expect to live up to 82 years. And we can credit our increasing expected lifespan to the improvement of modern medicine, safer environments, and overall better living conditions.
But, we have not increased our health expectancy. Aging is the cause of almost all diseases, and diseases are what hinder healthy life expectancy. So, how do we stop aging? First, we need to understand why people age.
Why Do We Age?
There’s the obvious factors, such as: our environment, sleep, diet, and exercise. We also have a biological clock, meaning that as humans, we are genetically programmed to die. Our biological age refers to how old our own cells really are and therefore, our real age. Biological age varies based on our lifestyles. This is different from our chronological age, which is irreversible and does not depend on our habits.
Telomeres & Senescent Cells:
Cell replication occurs in a cell every 300 to 500 days when the cell dies and is then replaced by a new cell. There are protective caps on the end of our DNA sequences called telomeres, which aid in cell replication to ensure that no genes are lost in the replication process. We can compare these telomeres to the small plastic cylinders on the tips of shoelaces. Eventually, when those tips fall off, the shoelace starts to fall apart too. This is what happens in our cells. As we get older, the telomeres shorten with each cell division, until they reach their end and can no longer divide anymore. This removes the protection from our cells’ DNA and enables disease and aging.
But, there’s more. Senescent cells, aka “zombie cells” are cells that were once healthy but have been damaged or their DNA has been mutated. To avoid passing that damage onto their daughter cells, they stop replicating. The immune system cleans them up at first, but over time the system stops responding, so these senescent cells accumulate in our bodies as we age. This is attributed to be an effect of the shortening of telomeres. The accumulation of senescent cells can lead to a major increase in our biological age, causing problems such as cataracts.
Free Radicals: chemicals which are naturally found in your body.
A free radical comes to be when a molecule or atom either gains or loses an electron. When a weak bond between an atom splits, it creates a free radical which goes looking for an electron. The free radical attacks the nearest molecule to steal an electron in order to stabilize itself, causing a chain reaction of that molecule doing the same thing. This is important to normal cell processes to neutralize viruses and bacteria. But, high levels of these free radicals can become a threat to cell components. This chain reaction can be exhausting for your body. Free radicals are throught to play a role in aging. They are associated with diseases such as cancer, Alzheimer’s, and Parkinson’s disease, but little is known about their role in human health.
How Do We Combat Aging?
There are many ways to solve the root causes of aging, just as aging is caused by many factors.
Caloric Restriction:
The first and most concrete method for longevity is composed of diet and exercise, and is called autophagy. This is a natural way to clean out unwanted components in cells, like senescent cells. One way to go through autophagy is by going on a ketogenic diet, which cuts out all carbs, forcing your body to fuel itself on fat. Other ways include intermittent fasting, and exercise. Through autophagy, your body is able to get rid of what it needs to get rid of, while adding health benefits. It decreases insulin resistance and your chance of getting cancer and other infectious and inflammatory diseases. Ultimately, this decreases aging rates.
Antioxidants:
Antioxidants are known to neutralize free radicals. The body naturally creates them, but these aren’t enough. So, we can also get them through our diet. There are many types of antioxidants, including Vitamin E, Vitamin C, and beta-carotene. Some foods that are high in antioxidants include green tea, ginger, berries, nuts, broccoli, garlic, and more. Antioxidants are able to shut down free radicals and because of this, scientists belive taking antioxidant supplements could have the potential to increase both lifespan and health-span. However, taking antioxidants will not guarantee a longer life, as many studies have been conducted to prove this theory and no definite results were found.
Stem Cells:
Perhaps one of the most effective forms of anti aging is through stem cell rejuvination.
All cells have different functions throughout the body. Once a cell is assigned a type at a baby’s birth, it functions as it should, and cannot change to a different type of cell with a different function. However, there is one type of cell that is flexible, and has the ability to function as different types of cells based on your body’s needs. These cells are stem cells, which come from babies, and are found in embryos, placenta, and umbilical cords. Baby’s stem cells are the most versatile, because a baby’s cells are still learning what to do when a they are born. Adult stem cells, found mainly in bone marrow or fat, are somewhat different because although they can become many different types of cells, they can’t become every type.
Scientists have discovered that genetic reprogramming can be used to program adult stem cells back to an embryonic state. These cells are called induced pluripotent stem cells, which act in the same way as young stem cells. Essentially, this tricks the cell aging process.
Advances in Longevity:
There are many companies currently working in human longevity research. They all take different approaches but their end goal is the same. Here’s a few:
Human Longevity is a biotechnology firm using machine learning in medicine to create a potential for longer and healthier lifespans. Its product “Health Nucleus” applies machine learning to produce personalized health assessments from a human’s DNA sequence.
Samumed is not based on stem cell therapy, but rather on the Wnt pathway, which is an aging-related signaling pathway. The pathway is involved in regulating the self-renewal of adult stem cells and proliferation. The company focuses on the Wnt pathway in order to restore diseased tissues. They develop therapies like small-molecule, tissue-level drugs aimed at treating degenerative diseases and many forms of cancer.
Is It Ethical?
The ethics of human longevity are a long and complicated debate, which I will go into in another article. But to sum it up, let’s explore a valuable question: does human longevity decrease the value of life? I would argue that if done ethically, it does not. If we are simply trying to maximize the number of healthy years that we spend on this planet, then longevity can be regarded as a very fancy way of taking care of yourself and your health. Like I said, it’s about living, not just existing.
Key Takeaways:
- The goal of longevity is not only to increase our lifespans, but also our health-spans.
- Biological aging is caused by many factors, including telomere shortening, senescent cells, and free radicals.
- Aging can be combatted through diet. Autophagy and increased intake of antioxidants can help decrease aging rates.
- Many companies are currently working on longevity related medicines to combat diseases through both the use of stem cell rejuvenation and Artificial Intelligence.
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